One person says that the potential energy of a particular book kept in an almirah is 20 J and the other says it is 30J. Is one of them necessarily wrong?

One person says that the potentil energy of a particular book kept in an almirah is 20 J and the other says it is 30J. Is one of them necessarily wrong?

The gravitational potential energy of a two particle system is derived in this chapter as U=-(Gm_1m_2)/r . Does it follow from this equation that the potential energy for r=oo must be zero? Can we choose the potential energy for r=o to be 20 J and still use this formula? If no what formula shoud be used to calculalte the gravitational potential energy at separation?

Two neutral particles are kept 1m apart. Suppose by some mechanism some charge is transferred from one particle to the other and the electric potential energy lost is completely converted into a photon. Calculate the longest and the next smaller wavelength of the photon possible. h=6.63xx10^(-34)Js .

A book of mass 1 kg is raised through a height .h.. If the potential energy increased by 49 J, find the height raised.

Two discharge tubes have identical material structure and the same gas is filled in them. The length of one tube is 10cm and that of th other tube is 20cm. Sparking starts in both the tubes when the potential difference between the cathode and the anode is 100 V . If the pressure in the shorter tube is 1.0 mm of mercury, what is the pressure in the longer tube?

A silver ball of radius 4.8 cm is suspended by a thread in a vacuum chamber, Ultraviolet light of wavelength 200nm is incident on the ball for some time during which a total light energy of 1.0 xx 10^-7 J falls on the surface. Assuming that on the average one photon out of every ten thousand is able to eject a photoelectron, find the electric potential at the surface of the ball assuming zero potential at infinity. What is the potential at the centre of the ball?

Take three different colour sheets , place one over the other and draw a triangle on the top sheet. Cut the sheets to get triangles of different colour which are identical. Mark the vertices and the angles as shown. Place the interior angles angle1,angle2 and angle3 on a straight line, adjacent to each other, without leaving any gap. What can you say about the total measure of the three angles angle1,angle2 and angle3 ? Can you use the same figure to explain the ''Exterior angle property'' of a triangle ? If a side of a triangle is stretched, the exterior angle so formed is equal to the sum of the two remote interior angles.

One end of a rod length 20cm is inserted in a furnace at 800K. The sides of the rod are covered with an insulating material and the other end emits radiation like a blackbody. The temperature of this end is 750K in the steady state. The temperature of the surrounding air is 300K. Assuming radiation to be the only important mode of energy transfer between the surrounding and the open end of the rod, find the thermal conductivity of the rod. Stefan constant sigma=6.0xx10^(-1)Wm^(-2)K^(-4) .

In a thermodynamic process, pressure of a fixed mass of a gas is changed in such a manner that the gas releases 20 J of heat and 8 J of work is done on the gas. If the initial internal energy of the gas was 30 J , what will be the final internal energy ?

The potential energy of a certain spring when streched by a distance x is 20J. The amount of work required to strech it through an additional distance x is: